The present invention relates to an image-reading apparatus comprising a combination of an image scanner and a host computer, utilized for an electronic filing system. The present invention also relates to an image-reading apparatus devised to be capable of transferring an image data to a host computer without losing it, even if an intervention is made to stop or suspend temporarily especially while the apparatus is feeding original paper sheets continuously.
Image-reading apparatuses provided with scanners for reading images have been in use for a long while as apparatuses to read a variety of original paper sheets in large volume for a purpose of electronic filing. The scanners feed a variety of original paper sheets, read images thereon, and output image data. A system is normally composed for the purpose of storage, control, retrieval, and so on of image data obtained by the scanner, by combining it with a host computer utilizing a personal computer. The system carries out an exchange of information signal between the scanner and the host computer via an interface.
In this kind of combination of a scanner and a host computer, it usually takes a longer time for transferring a read-out image data from an interface to the host computer as compared to a time spent for reading the image in a sheet of original paper. Thus, a processing time for a sheet of original paper is dependent upon the former, i.e. the transferring time. It is effective to provide two buffers immediately before the interface in order to accelerate the processing speed. In other words, it is possible to speed-up the processing, if a writing of read-out image and an output to the host computer are repeated alternately while switching these buffers, so as to absorb a difference between the reading time and the transfer time.
In the case of providing two buffers, a buffer A and a buffer B, data of a original paper sheet, of which an image has been read, is written in one of the buffers, i.e. the buffer A, whereas an image data of another original paper sheet, which has been fed a moment ahead of the original paper sheet being written, is output from the other buffer B to the host computer through the interface. In other words, even though the original paper sheets are read by the image-reading unit one at a time in a feeding order, the read-out data is not transferred immediately. Instead, an image data of the previous original paper sheet is output to the host computer from the other buffer B, while a subsequent original paper sheet is being read and written in the buffer A.
There are occasionally cases with the image-reading apparatus that require processing of a large volume of original paper sheets by feeding them consecutively. The operation is suspended, when original paper sheets loaded on a paper feeder of the scanner are rearranged, when new original paper sheets are additionally loaded, or if a trouble immerges with the apparatus. The suspension takes place when the host computer sends a suspending command, or the suspension can be made with a switch provided on the scanner side for the purpose of a temporary suspension. It is also feasible to temporarily suspend the scanner alone, or to stop operation of the entire system.
However, when a suspension is made in a mode of continuous feeding of the original paper sheets, the apparatus stops while the image data of the original paper sheet fed previously has still not as yet been output completely from the buffer B, even if the operation is suspended at such a point of time that a reading is completed for a original paper sheet whose image is being read. Hence, the image data will be lost.
That is, in the case of providing two buffers, the buffer A and the buffer B, the previously written image data of original paper sheet is output from the buffer B, while another data of original paper sheet is being written in the buffer A. After a completion of the output from the buffer B, an image data of the subsequent original paper sheet is output from the buffer A, and a data of the following original paper sheet is written in the buffer B. Therefore, if the operation stops after a completion of reading the image on the fed original paper sheet, i.e. the completion of writing the image into the buffer A, the other buffer B suspends an output before completing a process of the whole image data.
As described, when the operation is suspended in the mode of continuous feeding of the original paper sheets, the reading of image and the writing it into the buffer are brought into completion so far as the original paper sheet already fed into the image-reading unit is concerned. It is therefore possible to write the entire image data of the original paper sheet into the buffer. However, another buffer, which has already received the image data from the previously fed original paper sheet, is not able to output the entire image data within a time period between the suspending command and the completion of writing the subsequent original paper sheet.
As has been described, the image-reading apparatus of the prior art loses an image data every time the apparatus is suspended of operation, thereby giving rise to a problem of reliability in the image reading.
A problem to be solved in the present invention is to provide a highly reliable image-reading apparatus capable of outputting entirely an image data that it reads from a original paper sheet without losing it, even if the operation is suspended during a continuous reading.
The present invention relates to an image-reading apparatus for feeding a paper, reading an image on the paper, and outputting the read-out image data to an external apparatus. The image-reading apparatus comprises:
(a) a paper feeder for feeding a stack of papers one after another;
(b) an image-reading unit for reading an image on the paper fed from the paper feeder;
(c) an image data output unit for outputting the read-out image data to the external apparatus;
(d) a plurality of buffer units provided between the image-reading unit and the image data output unit, wherein an image data is written by the image-reading unit, and wherefrom the image data is read and forwarded to the image data output unit; and
(e) an operation suspending controller for suspending operation of the paper feeder and the image-reading unit from taking another paper subsequent to a paper under a process of being read, and also for stopping operation of the image-reading apparatus only after the image data output unit outputs all of image data from the buffer unit that contains the image data written already by the image-reading unit, when an operation suspending command is given to the image-reading apparatus.
The foregoing structure can prevent the apparatus from suspending the operation until all of the image data is output from the buffer unit, in which the image data is being written from the paper already in a process of being read, even if the apparatus receives a suspending command, thereby avoiding a loss of the read-out image data.